According the research studies of the inventors, conventional fracturing stimulation method that is identical or similar to that used in conventional oil and gas layers is commonly used for non-conventional oil and gas layers, such as tight oil and gas, shale gas, and coal-bed methane. The conventional fracturing stimulation method uses large-scale water-base fluid with proppant, therefore mainly having the following problems:
1. A large amount of fracturing fluid having poor compatibility with the strata is needed and tends to pollute the strata. Large amount of flow-back fluid with complex composition is left after fracturing, and detoxification of the disposal is very difficult and expensive, resulting in pollution of the environment.
2. The stimulation of oil and gas is poor. In conventional fracturing, there is only point contact between the fracture surface and the spherical ceramic proppant, which is easily crushed and embedded into the soft strata, resulting in short effective duration of stimulation. Moreover, as the proppants are separated from each other, small particles in the proppants tend to move and flow back, causing complex and dangerous issues such as blocking and abrading the pipeline system laid on the ground, under the ground and at the wellhead.
3. Large hydraulic horsepower is needed. For example, in a horizontal shale gas well with a vertical depth of 3000 meters and a horizontal length of 1000 meters, over 20,000 HHP of hydraulic horsepower is needed for the fracturing trucks in conventional staged fracturing operations.
4. Large well site is needed. Lots of conventional fracturing equipments and accessorial equipments are used to transport and store materials for fracturing, oil, proppant, water, etc., thus occupying large well site.
5. High risk of environmental damage. The conventional fracturing uses large-scale water-based fluid and proppant producing a mass of flow-back fluid after fracturing, causing costly disposal detoxification and reuse of the flow-back fluid and serious pollution to the natural environments such as water, land air, and so on. The massive fracturing using water-based fluid for coal-bed methane or gas hydrate in the shallow strata would bring geological disasters, such as land collapse, landslide, earthquake, etc.
6. High cost of exploitation. Using conventional fracturing stimulation in non-conventional oil and gas layer has the disadvantages of needing large amount of fracturing fluid, large hydraulic horsepower, large well site, high environmental expenses, and short effective duration of stimulation, resulting in high cost of exploitation, therefore limiting rich non-conventional oil and gas to be mined in an effective, environmentally friendly and massive way. The rich non-conventional oil and gas include tight oil and gas, shale gas, coal-bed methane, gas hydrate and etc.